Spark-gap indicator



T. F. JOHNSON, In.

SPARK GAP INDICATOR.

APPLICATION FILED AUG. 16, 19I9.

1 344E042, Patented June 22, 1920.

2 SHEETSSHEET 1.

v INVENTOR WITNESSES N .7 fi'Johiwon 7 (Qim/mg4 go BY T. F. JOHNSON, In.

SPARK GAP INDICATOR.

v APPLICATION FILED AUG-1B. 1919.

Patented June 22, 1920.

2 SHEETS-SHEET 2- W====Ei INVE'NTOR WITNESSES @AM/M v BY ATTORNEY UNITED STATES PATENT OFFlCE.f

'IOMLINSON FORT JOHNSON, JR.', 0F ATLANTA, GEORGIA.

SPARK-GAP mmcarox.

Specification of Letters Patent. i Patented J 11119 22, 1920,

I Application filed August 16, 1919. Serial Ro. 318,025.

rents the insulators employed not infre-.

quently break down, sometimes to only a small extent, but if such small degrees of breakdown be allowed to continue a serious breakdown may occur, putting the line entirely out of commission so that customers may be deprived of current for a comparatively long period of time. If a weakening of the insulation be made apparent it may.

be localized and corrected promptly without in any manner impairing the service. It is possible to discover incipient breakdowns by suitably testing the --lines from time to time but this requlres the attention of a force of men for doing the testing.

In high tension transmission lines which may carry voltages up to 110,000 volts more or less, it is customary to employ suspension types of insulators in strings each containcapable of withstanding high tension currents, known as the pin-type insulator. In either type of insulator breakdowns, occur which usually are small at first, affecting possibly a single element of the insulator or two or more elements without breaking down the insulator as a whole orall at once, although the incipient breakdown, if neglected, may result in the total destruction of the insulating qualities of the insulator.

In accordance with the invention, each insulator is provided with a spark gap, or such spark gap "may be multiplied so that every separate element of the insulator is provided with a spark gap. With such an arrangement thespark gap, which is silent under normal conditions, becomes audible,

or audible and visible, thereb giving warnin that the insulating qualities of the insulator will deteriorate and needprompt attcntion to revent interruption of service. Such an in icator is made a permanent part of the installation, requires no attention and is entirely automatic in its operation. All that is required is occasional inspection, without the necessity of any testing, for simple observation, will. show to an inspector whether or not the installation is in proper condition so far as the insulators are concerned.

The invention will be best understood from a consideration of the following'detailed description taken in'connection with the accompanying drawings forming part of this specificatiomw'ith the understanding, however, that the invention is not confined to any strict conformity with the showing of the drawings, but may be changed and modified so long as such changes and modifications mark no material departure from the salient features of the invention as expressed in the appended claims.

In the drawings Figure 1 is an elevation of a string of suspension insulators with each unit provided with a spark gap.

Fig. 2 is a similar View showing but one of the units provided with a spark gap.

Fig. 3 is a view partly in elevation and partly in diametric sectlon, of a pin-type lnsulator provided with a spark gap for each unit.

Fig. 4 is a similar view showing but one of the units of the pin-type insulator proing a suitable number of insulators in series. There is also another type of insulator ided with a spark gap.

Fig.5 is a view of an element of a string .of suspension insulators provided with a than the other views showing an arrangement of the spark gap.

Considering first suspension insulators, there is shown in Figs.- 1 and 2 a string A of suspension insulators made up, in the par- .ticular showing of the drawings, of eight insulator elements, numbered consecutively from 1 to 8 and extending between a cross beam 9 and a'line wire orconductor 10, which latter may be considered as carrying alternating current at 110,000 volts.

For

such a voltage eight insulators constitute the proper number between the line wire and the supporting structure, such arrangement having been established by practice. Each insulator comprises a metallic cap 11 and a porcelain part 12, neither of which require any special description or showing, since they may be of standard construction.

Such a string of suspension insulators is, in eflect, a string of condensers, the porcelain parts of the insulator being the dielectric and the metallic couplings between the insulators constituting'the plates of the condensers. It is not necessary that these couplings be actually metallic so long as they are of conducting or semi-conducting material.

The spark gap structure may comprise a conductor 13 connected to and supported on the cap 11 by a block 14. of insulating material. Theronductor 13 at the end remote from the block 14 terminates in a ball or enlargement 15 brought into suiiiciently near approach to the insulating or conducting element of the insulator to answer the purposes of the invention. Some types of insulators are provided with grooves between the cap 11 and the porcelain member 12 and such groove may be utilized asa seat for a broken ring 16 of metal with a series of bulbs or blocks 17 of insulating material thereon for holding the ring 16 in place but out of actual contact with the porcelain or conducting element. Extending from the ring 16 is a conductor 18, which may be conveniently made of wire, and terminating in a ball 19 which may be so situated as to be in proper relation to the cap 11. Still other types of insulators are provided with metallic spiders 20, as shown in Fig. 8, taking the. place of the cap 11 and carried by the porcelain member 12. Also carried by the porcelain member 12 is a conducting rod or wire 21 terminating in a ball 2 andbrought into sparking distance with relation to the spider 20. The several examples given are sufiicient to show that the invention is adaptable to a great variety of insulators.

Now, since a strin of insulators-such as shown in Fig. 1 or ig. 2 is really a string of condensers in series, the electric char e on the various caps of the insulators ecreases from the line wire 10to the cross arm 9, that is, the ca on the insulator 1 has a certain charge on it, that of the insulator 2'has a less charge and the other caps have progressively smaller charges. However, on any given line with a given number of insulators in a string, the charge on corresponding caps in every string, when all the insulators are good, is always e ual. For instance, the charge on the cap 0 insulator 1, when the insulator is good, is equal to a certain amount. If the insulator 1 becomes defective the charge on the cap thereof will insulated from the head of the insulator,

the gap may be set at such a distance that it will be noiseless and will not fire so long as the charge on the head of the insulator to which it is attached is correct. By properly setting the gap an increase in the charge on the head of the insulator will cause it to jump across the gap. When the insulator is but slightly defective the arc across the gap cannot be seen but can be heard. When the insulator becomes more defective the arc across the gap can be both seen and heard.

In Fig. 1 it isassumed that such spark gaps as have been described are established on the cap or head of each insulator with the spark gaps properly set. Any defect in .any insulator will be indicated by the spark gap on the head of that insulator firing or ecoming noisy. This firing is only a small brush discharge and the arcs, while very string or stack of insulators in series between the line and the supporting structure, and in case of some one or more of .the insulator units becoming, defective the particular units are indicated. However, similar results can be obtained by establishing properly adjusted gaps in any number of individual insulators on a string with such number of gaps less'than the total number of individual insulators. If one insulator in a string is selected and a spark gap established on this insulator and any individual insulator or unit develops a defect the voltage across the gap is raised, thus causing the string of insulators to become noisy or visibly fire at the spark gap. This won (1 not necessarily indicate that the individual insulator or unit to which the gap was attached was defective but would definitely indicate that some one or more of the units of the string were defective.

In the structure shown in Figs. 3, 4 and 9 there appears a pin type of insulator including a pin 23 on which is mounted a series of insulating units 24.- surmounted by a line conductor 10. The units 24' are of the nested petticoat type with each inner unit entering the next larger one and united thereto by a suitable cement 25, which cement may be of semi-conducting type.

Fast, in the form shown in Fig. 3, to each porcelain petticoat beyond the one carrying the line conductor 10, is a block 26 of insulating material carrying a metallic finger 27 terminating close to the cement 25 so as to provide a spark gap, which latter, of course, must be properly set. In the form shown in Fig. 4 the same result is obtained by the use of a single conducting finger 27,

the arrangement being otherwise the same applies to the other.

What is claimed is 1. A high tension alternating current transmission line provided with insulators for supporting the line, said insulators having permanent spark gaps each set to remain silent under normal conditions of transmission and to sensibly respond to a lessening of the insulating qualities of the insulators as a whole.

2. A high tension alternating current transmission line provided with insulators for supporting the line and each comprising a plurality of insulating units, and permanent spark gaps in the insulators each set to remain silent under'normal working conditions and to sensibly respond to a lessening of the insulating qualities of the insulators.

3. In a high tension alternating current transmission line, an insulator formed of a series of insulating units with intervening portions having electrical conducting qualities, a spark gap structure comprising a metallic member carried by an insulator unit and in proximity to and separated from a conducting part of the insulator by a distance too great to admit the passage, in an audible manner, of current at normal voltage.

4. A high tension alternating current transmission line provided with insulators for the line, each consisting of a plurality of condenser units, and spark gaps carried by the insulators and adjustable for the bridging of the gaps by the line current when the "oltage at the gaps becomes abnormally high, whereby to indicate to an obserx er that abnormal conditions are present.

5. A high tension alternating currenttransmissionline having insulators for the line, each insulator comprising a plurality of condenser units, and means on an insulator for sensibly indicating to an observer iliminished insulating qualities of the insuator.

6. A high tension alternating current transmission line having insulators supporting it, with each insulator comprising insulating units in series with conducting material alternating with the units, and conducting means carried by an insulating part of the insulator and approaching but stopping short of a conducting part of the insulator to provide a spark gap resistent to bridging by current at normal.

voltage and responsive to current of a higher voltage, whereby on the development of a defect in the insulator sensible evidence of the defect is imparted to an ob-- server.

7. A high tension alternating current transmission line provided with insulators carrying it, each insulator comprising alternate insulating and conducting members, the insulators each having conducting means approaching but stopping short of one or more of the conducting members of the insulator to provide a spark gap for a discharge across the spark gap on a rise of voltage above the normal at said spark gap.

8. A high tension alternating current transmission line provided with insulators carrying it, with each insulator composed of a series of alternately arranged insulating and conducting members and each insulator provided with a conductor carried by an insulating member and stopping short of the next conducting member in order to provide a spark gap adjusted to prevent a discharge across the gap of current at normal voltage at the gap and permit a discharge of current of higher voltage.

9. A high tension alternating current transmission line provided with insulators carrying it and each consisting of a series of condenser units with each unit provided with a spark gap resistent to the passage of normal current and responsive to the pas sage of current of higher-voltage than normal due to the break-down of any one or more of the condenser units.

In testimony that I claim the foregoing as my own, I have hereto aiiixed my signature.

TOMLINSON FORT JOHNSON, JR. 

